Electric vehicle charging to reduce utility cost

ABSTRACT

A method for controlling the charging of one or more electric vehicles at one or more charging stations in a geographic locality includes determining if the charging event of an electric vehicle of the one or more electric vehicles increases a demand billing rate. The demand billing rate may be a cost per unit of energy in the locality. The method also includes charging the electric vehicle at the charging event such that the demand billing rate is not increased.

TECHNICAL FIELD

The current disclosure relates to systems and methods of chargingelectric vehicles to reduce utility cost. In particular, the currentdisclosure relates to a control system that controls the charging of anelectric vehicle based on the prevailing utility rates in an area.

BACKGROUND

An electric vehicle uses an electric motor for propulsion. Electricvehicles include all-electric vehicles where the electric motor is thesole source of power, and hybrid vehicles that include another powersource in addition to the electric motor. In an electric vehicle, energymay be stored in batteries to power the motor. When the stored energydecreases, the batteries may be recharged using an external powersupply. Typically, the size, architecture, chemistry, etc. of thebatteries determine its range (i.e., the distance the vehicle can travelbetween recharges) and the time it takes to recharge the batteries(recharge time).

In applications where it is important to charge the batteries quickly,fast-charge batteries may be used. Fast-charge batteries may be chargedto substantially full capacity quickly at high power levels (i.e., rateof energy transfer). The range of fast-charge batteries are typicallylow, therefore, these buses are recharged periodically (e.g., between5-20 miles). The cost of energy in some geographic locations vary withthe rate of energy consumption. In some applications, significantsavings may be realized by controlling the charging of the vehicle basedon prevailing utility cost.

Embodiments of the current disclosure may alleviate some of the problemsdiscussed above and/or other problems in the art. The scope of thecurrent disclosure, however, is defined by the attached claims, and notby the ability to solve any specific problem.

SUMMARY

Embodiments of the present disclosure relate to, among other things,systems and methods for controlling the charging of electric vehiclesbased on utility costs. Each of the embodiments disclosed herein mayinclude one or more of the features described in connection with any ofthe other disclosed embodiments.

In one embodiment, a method for controlling the charging of one or moreelectric vehicles at one or more charging stations in a geographiclocality is disclosed. Each electric vehicle of the one or more electricvehicles may be configured to be charged at a charging station of theone or more charging stations at a charging event. The method mayinclude determining if the charging event of an electric vehicle of theone or more electric vehicles increases a demand billing rate. Thedemand billing rate may be a cost per unit of energy in the locality.The method may also include charging the electric vehicle at thecharging event such that the demand billing rate is not increased.

In another embodiment, a method for charging an electric bus at acharging station is disclosed. The method includes electrically couplingthe bus at the charging station to begin a charging event, anddetermining a maximum amount of energy (E_(MAX)) that can be consumed bythe charging station in a reference time period without increasing ademand billing rate. The demand billing rate may be a cost per unit ofenergy consumed by the charging station. The method may also includedetermining the total amount of energy already consumed (E_(USED)) bythe charging station in the reference time period. The method may alsoinclude estimating the energy needed (E_(NEED)) by the bus during thecharging event and determining if E_(NEED) exceeds (E_(MAX)−E_(USED)).The method may further include providing an amount of energy equal toE_(NEED) to the bus if E_(NEED) does not exceed (E_(MAX)−E_(USED)).

In yet another embodiment, a charging station for an electric vehicle isdisclosed. The charging station includes a charging head configured toelectrically couple with and charge an electric vehicle during acharging event and a control system. The control system may beconfigured to determine if the charging event will increase a demandbilling rate. The demand billing rate may be a cost charged per unit ofenergy consumed by the charging station. The control system may also beconfigured to charge the electric vehicle at the charging event suchthat the demand billing rate is not increased.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of thepresent disclosure and together with the description, serve to explainthe principles of the disclosure.

FIG. 1 is an illustration of an exemplary electric bus;

FIG. 2 is a schematic illustration of the electric bus of FIG. 1operating in a geographic area;

FIG. 3A is a flow chart illustrating an exemplary method of charging theelectric bus of FIG. 1 at a charging station;

FIG. 3B is a flow chart illustrating another exemplary method ofcharging the electric bus of FIG. 1; and

FIG. 4 is a schematic illustration of en exemplary energy consumptioncurve of the charging station.

DETAILED DESCRIPTION

The present disclosure describes a control system and a method ofcontrolling the charging of electric buses to reduce utility cost. Whileprinciples of the current disclosure are described with reference to anelectric bus, it should be understood that the disclosure is not limitedthereto. Rather, the systems and methods of the present disclosure maybe used to control the charging of any electric vehicle (one or moretaxis, etc.).

FIG. 1 illustrates an electric vehicle in the form of a low-floorelectric bus 10. Electric bus 10 may include a body 12 enclosing a spacefor passengers. In some embodiments, some (or substantially all) partsof the body 12 may be fabricated using composite materials to reduce theweight of bus 10. As is known in the art, in a low-floor bus, there areno stairs at the front and/or the back doors of the bus. In such a bus,the floor is positioned close to the road surface to ease entry and exitinto the bus. In some embodiments, the floor height of the low-floor busmay be about 12-16 inches (30-40 centimeters) from the road surface.Body 12 of bus 10 may have any size, shape, and configuration.

Bus 10 may include an electric motor that generates power for propulsionand a battery system 14 that provides power to the electric motor. Insome embodiments, the battery system 14 may be positioned under thefloor of the bus 10. The batteries of battery system 14 may have anychemistry and construction. In some embodiments, the batteries may belithium titanate oxide (LTO) batteries. In some embodiments, thebatteries may be nickel manganese cobalt (NMC) batteries. LTO batteriesmay be fast-charge batteries that may allow the bus 10 be recharged tosubstantially its full capacity in a small amount of time (e.g., aboutten minutes or less). In this disclosure, the terms “about,”“substantially,” or “approximate” are used to indicate a potentialvariation of 10% of a stated value.

Due to its higher charge density, NMC batteries may take longer tocharge to a comparable state of charge (SOC), but NMC batteries mayretain a larger amount of charge and thus increase the range of the bus10. State of charge (SOC) is the equivalent of fuel level in ahydrocarbon (e.g., gasoline, diesel, etc.) powered vehicle. SOCindicates the amount of residual energy in the battery system 14 of thebus 10. The SOC of a battery system 14 (or bus 10) is defined as theavailable energy capacity expressed as a percentage of its ratedcapacity or present capacity (i.e., taking age into account). The unitsof SOC are percentage points, where an SOC of 0% indicates that thebattery system 14 is completely empty and an SOC of 100% indicates thatthe battery system is full. In some embodiments, battery system 14 mayinclude batteries of multiple chemistries. For instance, some of thebatteries may be LTO or NMC batteries, while other batteries may haveanother chemistry (for example, iron-phosphate, lead-acid, nickelcadmium, nickel metal hydride, lithium ion, zinc air, etc.). Some of thepossible battery chemistries and arrangements in bus 10 are described incommonly assigned U.S. Pat. No. 8,453,773, which is incorporated hereinby reference in its entirety.

Although the battery system 14 is illustrated and described as beingpositioned under the floor of the bus 10, this is only exemplary. Insome embodiments, some or all of the batteries in battery system 14 maybe positioned elsewhere on the bus 10. For example, some of the batterypacks may be positioned on the roof of bus 10. As the battery system 14may have considerable weight, integrating the battery system into thefloor of bus 10 may keep its center of gravity lower and balance weightdistribution, thus increasing drivability and safety.

A charging interface 16 may be provided on the roof 18 of the bus 10 tocharge the batteries of the battery system 14. The charging interface 16may include a charging blade 16A and an alignment scoop 16B. Thecharging blade 16A may include electrodes that are electrically coupledto the battery system 14. The alignment scoop 16B may include a pair ofcurved rails, positioned on either side of the charging blade 16B, thatforms a funnel-shaped alignment feature. The charging interface 16 mayengage with a charge head 30 (positioned within a charge head assembly40) of an external charging station 50 to charge the battery system 14.The charging station 50 may be provided at any location (bus depot, roadside, etc.) and may be powered by an electric utility grid.

To charge the bus 10, the bus 10 may be positioned under the overhangingcharge head assembly 40 of the charging station 50. When the bus 10 isthus positioned, the charge head 30 may descend from the charge headassembly 40 to land on the roof 18 of the bus 10. With the charge head30 resting on the roof 18, the bus 10 may be moved forward to engage thecharge head 30 with the charging blade 16A. As the charge head 30 slideson the roof 18 towards the charging blade 16A, the funnel-shapedalignment scoop 16B may align and direct the charge head 30 towards thecharging blade 16A. Details of the charge head 30 and the interfacing ofthe charge head 30 with the charging interface 16 are described incommonly assigned U.S. Patent Application Publication Nos. US2013/0193918 A1 and US 2014/0070767 A1, which are incorporated byreference in their entirety herein. Alternatively or additionally, bus10 may also include an on-board charging device to charge the batterysystem 14. The on-board charging device may include an auxiliary powergeneration device (such as, an internal combustion engine or a fuelcell) that generates power to charge the battery system 14.

FIG. 2 is a schematic illustration of a fleet of transit electric buses10 operating along several fixed routes 20 in a geographic area 70.Geographic area 70 may include any area (airport, university campus,city, town, county, etc.) that is serviced by the buses 10. The fleetmay include any number of buses 10. One or more charging stations 50 maybe positioned along the different routes 20 to charge the buses 10 thatcirculate on these routes 20 on a fixed schedule. The charging stations50 may be coupled to an electric grid that is supplied with energy(electricity) by a utility company that services the geographic area 70.When a bus 10 pulls up to a charging station 50, the charge head 30 (seeFIG. 1) of the charging station 50 engages with the charging interface16 of the bus 10 to charge its battery system 14. After charging, thecharge head 30 decouples from the charging interface 16 and the bus 10proceeds along its route 20. After completing the route 20 (or along itsroute), the bus 10 may pull into the same or a different chargingstation 50 for recharging. After recharging, the bus 10 may continue torepeat its fixed route 20. In some embodiments, the charging stations 50may be positioned such that they can service the buses 10 operating onseveral different routes 20.

In some embodiments, one or more of the charging stations 50 may alsoinclude an energy storage device 35 (capacitor, battery, etc.)electrically coupled thereto. The bus 10 may be recharged using energyfrom the grid, energy from the energy storage device 35, or using energyfrom both the grid and the device 35. In some embodiments, energy fromthe electric grid may be used to charge the energy storage device 35when the energy cost is lower, and this stored energy may be used tocharge a bus 10 when the energy cost is higher. Some possibleembodiments of such energy storage devices are described incommonly-assigned U.S. Patent Application No. 2015/0069970 A1 which isincorporated by reference in its entirety herein.

The utility company may charge the bus operator (or a transportationauthority operating a fleet of buses) for the energy consumed incharging the buses 10 based on a prevailing tariff schedule. The tariffschedule documents the cost per unit of electricity (for example, $/kiloWatt hr.) as a function of several factors. These factors may vary withthe geographic area 70, and include variables such as the season, timeof use, rate of energy consumption (i.e., power), total energy consumed,voltage, etc. Typically, energy cost is higher when the demand forenergy is higher (e.g., Summer months, and times between 8 AM-10 AM, 4PM-6 PM, etc.) and lower when the demand is lower (e.g., Winter months,times between 10 AM-4 PM and 6 PM-8 AM, etc.). For a commercialconsumer, the energy cost may follow a tiered approach. That is, theenergy cost may change with the total power consumed. For example, totalpower consumption (per billing cycle) between 20 kilo Watts (kW) and 1Mega Watt (MW) may be charged at a first rate, between 1-50 MW may becharged at a second rate, and above 50 MW may be charged at a thirdrate.

The cost of electricity typically includes a “consumption charge” and a“demand charge.” The consumption charge accounts for the actual cost forthe generation of the consumed amount of electricity (e.g., fuel costs,etc.), and the demand charge accounts for fixed overhead costs. Althoughboth consumption and demand charges are part of every electricityconsumer's utility bill, residential customers usually pay one rate forelectricity service, covering both consumption and demand. This combinedcharge is possible because there is relatively little variation inelectricity use from home to home. However, for most commercial andindustrial energy users, both consumption and demand vary greatly.Commercial customers (such as, operators of electric buses and chargingstations) need large amounts of electricity once in a while. Forexample, some charging stations 50 charge a bus 10 at a relatively highenergy transfer rate of 400 kW for a few minutes (e.g., 3 minutes). Ifthis charging station 50 charges four buses in an hour, the chargingstation 50 is operational for only a small fraction of an hour (i.e.,operational for 12 minutes of an hour). Meeting such a customer demandrequires keeping a vast array of expensive equipment (transformers,substations, generating stations) on constant standby. These costsaccount for the demand charges.

Demand charges vary as a function of the rate at which energy isconsumed (i.e., power consumption). That is, the cost for 100 kWhr ofenergy will be higher if this amount of energy were consumed in one unitof time (unit of time=1 minute, 15 minutes, 30 minutes, etc.) than if itwere consumed over a longer time period (for example, in two units oftime). For example, the cost per unit of energy is lower if the rate ofenergy consumption (typically measured as the total energy consumptionfor a reference time period, e.g., 15 minutes) is below a certain value,and higher if the rate of energy consumption is above this value.Typically utility companies monitor the total energy usage for areference time period (e.g., 15-minute time window) to determine thedemand billing rate (i.e., cost/kW) for utility cost calculations. Insome geographic areas 70, the peak energy consumption in a 15-minutewindow in a billing cycle may be used to calculate the total energy costfor the entire billing cycle. For example, if during one 15-minutewindow during the billing cycle, the total energy consumption was 3times the average for the rest of the billing cycle, the total energycost for the entire billing cycle may be calculated at the higher rate(demand billing rate). The utility company may periodically revise thetariff schedule and communicate this revised schedule to thetransportation authority and other consumers.

A control system 60 may control the charging of the buses 10 based uponthe tariff schedule. The control system 60 may be positioned at anylocation (or distribute among multiple locations) and include one ormore computer systems or electronic devices interconnected together in awired or wireless manner. In some embodiments, the control system 60 maybe located at a charging station 50. In some embodiments, control system60 may reside in one or more computer servers in the offices of thetransportation authority or at another site remote from a chargingstation 50. The control system 60 may be configured to receive data(wirelessly or over a wired network) from, among others, some or all ofthe buses 10 operating in area 70, charging stations 50, the utilitycompany, and the transportation authority. The control system 60 mayalso be configured to store data, perform computations, and relay dataand/or instructions to some or all of the buses 10 and/or the chargingstations 50. In some embodiments, the control system 60 may also includeinput devices (such as, for example, keyboards, disk/CD/DVD readers,memory card readers, etc.) configured to input data into the controlsystem 60, and output devices (display devices, printers,disk/CD/DVD/memory card writers) configured to output data andinformation. The control system 60 may also be configured to store data62 and other information, and perform computations on the stored andreceived data.

The data 62 stored in the control system 60 may include the prevailingtariff schedule in geographic area 70. Data 62 may also include, amongothers, information regarding the routes 20, buses 10, drivers, and thepassengers. Information regarding the routes 20 may include GPSlocations of the different routes 20, bus schedules (bus times alongdifferent routes), distance of the routes, distance between stops alonga route 20, location of charging stations 50 along the routes 20, etc.Information regarding the buses 10 may include bus identifyinginformation, energy storage capacity (e.g., based on size of batterysystem 14, age of battery system, etc.), expected energy consumptiondata (e.g., based upon historic energy consumption (miles/kWhr), theage, and state of repair of the bus), etc. of the buses 10. Informationregarding the drivers may include the driving habits of the driversbased on historical data. And, information regarding the passengers mayinclude historical data on the expected number of passengers atdifferent stops along a route 20 at different times.

In some embodiments, the data 62 stored in the control system 60 mayinclude a default charging schedule for the buses 10. Among otherinformation, the default charging schedule may indicate the chargingtimes (time of day) for different buses, the amount of energy to provideto the buses, and the charging rate (rate of charging) to be used duringa charging event. In fast-charge applications, it may be desirable tocharge a bus quickly. Therefore, in some embodiments, the chargingschedule may list a fast charging rate (e.g., fastest charging rate thatcan be safely employed by the charging station) as the default chargingrate. In some embodiments, the default charging schedule may bepreprogrammed into the control system 60. In some embodiments, thedefault charging schedule may be determined, or revised as needed,based, for example, on information of the route 20 and the buses 10 thatoperate on the route 20. In some embodiments, the default chargingschedule may specify charging a bus 10 at the beginning or completion ofits route 20. For example, a transit bus 10 operating on a cyclic fixedroute (e.g., a 5 mile loop around a school campus) may be charged at acharging station 50 at the beginning or the end of its route.

In some embodiments, the default charging schedule may indicate charginga bus 10 to its maximum state of charge (SOC) every time the bus 10 ischarged at a charging station 50. That is, with reference to the exampleabove, even if the bus 10 that operates around a 5 mile loop has 80% SOCwhen it pulls in for charging, and the bus consumes only about 10% ofits SOC to complete the 5 mile route, the bus 10 may be charged to about100% SOC during each charging event. However, in some cases, chargingthe bus to 100% SOC may increase the total energy consumed by thecharging station 50 during a time of reference that the utility companyuses to monitor power consumption (e.g., 15 minute time window), andthus increase the demand billing rate at which utility cost iscalculated for the entire billing cycle. Therefore, in some embodiments,the control system 60 may revise or modify the default charging schedulebased on prevailing utility rates to minimize utility cost.

FIG. 3A is a flow chart of an exemplary method 100 used by controlsystem 60 to charge a bus 10 that docks with a charging station 50. Inthe discussion below, for the sake of simplicity, it is assumed thatgeographical area 70 includes only a single charging station 50 whichcharges multiple buses 10 operating in the area 70. However, as would berecognized by a person of ordinary skill in the art, the methoddescribed below is broadly applicable to a geographical area 70 havingany number of charging stations 50 charging the buses 10. Further, inthe discussion below, an exemplary time of reference of 15 minutes isused. However, in general, the time of reference can be any time period(e.g., 10 min, 30 min, 1 hour, etc.). FIG. 4 is an exemplary schematicillustrating the energy consumed by the charging station 50 over time.In FIG. 4, times t₀ and t₁s indicate the start and end of a current timewindow 300, and time t_(i) indicates the current point of time. Sections310, 320, and 330 in the energy consumption curve of FIG. 4 representtime periods at which buses were charged (prior to the current timet_(i)), and plateaus 315, 325, and 335 illustrate time periods when thecharging station 50 was idle (i.e., buses were not being charged). Inthe discussion below, reference will be made to both FIGS. 3 and 4.

In method 100, the maximum amount of energy (E_(MAX)) that can beconsumed in the 15 minute time window 300 (or any other reference timeperiod (10 min, 30 min, 1 hr., etc.) used by the utility company)without triggering a rate hike is first determined (step 110). E_(MAX)may be an arbitrary value selected by the transportation authority thatoperates the buses, or it may be a value determined by some method. Insome embodiments, E_(MAX) may be calculated based on historic energyconsumption data. For example, previous billing data may indicate thatan average amount of energy consumption per hour was (for e.g.,) 120kWhr. Based on this information, E_(MAX) for the 15 minute time window300 may be determined as 120/4=30 kW. In some embodiments, E_(MAX) maybe determined based on a schedule optimization routine. For example,based on the schedule of the buses 10 operating in the geographic area70 and other factors (passenger load, cost, etc.), an optimizationalgorithm may determine E_(MAX) as the value of energy consumption thatoptimizes efficiency and cost. This predetermined value of E_(MAX) maybe programmed into control system 60.

The control system 60 may track the total amount of energy used(E_(USED)) by the charging station 50 during the 15 minute time window300 up to the current point of time t₁ (step 120). The control system 60may determine E_(USED) by summing the energy consumed by the chargingstation 50 between times to and tin the time window 300. In embodimentswhere the geographic area 70 includes multiple charging stations 50 forcharging buses 10, E_(USED) may be determined as the total energyconsumed by all the charging stations 50 in the time window 300 up tocurrent time

The control system 60 may then determine the amount of energy needed(E_(NEED)) by the bus 10 based on the default charging schedule (step130). In some embodiments, E_(NEED) may be determined based on theresidual SOC (i.e., SOC before charging begins) of the bus 10 and itsbattery capacity. In some embodiments, the bus 10 may inform (transmit,etc.) the control system 60 of its current SOC prior to, or after,docking with the charging station 50. In some embodiments, the bus 10may also indicate the capacity of its battery system 14 to the controlsystem 60. In some embodiments, the data 62 stored in control system 60may include information related to the battery capacity. In embodimentswhere the default charging schedule requires the bus 10 to be charged to100% SOC, in step 130, control system 60 may determine E_(NEED) as(1−residual SOC)×battery capacity. Similarly, in embodiments where thecharging schedule requires the bus 10 to be charged to a different SOC(e.g., 90% SOC), E_(NEED) may be calculated as 0.9×(1−residualSOC)×battery capacity.

The control system 60 may then determine whether E_(MAX) (i.e., maximumamount of energy that can be consumed in the reference time periodwithout triggering a rate hike) will be exceeded if the bus 10 isprovided with the amount of energy it needs (E_(NEED)) to satisfy thedefault charging schedule (step 140). That is, in step 140, the controlsystem 60 may determine if E_(USED)+E_(NEED)>E_(MAX) for the timeperiod. If it is not, then the bus 10 may be charged as per the defaultcharging schedule (step 150). That is, in step 150, the bus 10 may beprovided with an amount of energy equal to E_(NEED) at the defaultcharging rate.

If E_(USED)+E_(NEED) is determined to be greater than E_(MAX) in step140, then the control system 90 may determine the minimum amount ofenergy (E_(MIN)) needed by the bus 10 to complete its route (step 160).As explained previously, the control system 60 may have data 62 thatincludes information regarding the routes 20 of the buses 10 andhistorical data of the buses 10. Based on this information, in step 160,the control system 60 may determine how much energy is actually consumedby the bus 10 between two successive charging events. In embodimentswhere the bus 10 completes its route 20 and returns to the same chargingstation 50 for charging, the control system 60 may determine the energyconsumed by the bus 10 to complete its route 20. In embodiments wheregeographic area 70 includes multiple charging stations 50, and the bus10 charges at different charging stations 50 along its route 20, thecontrol system 60 may determine the amount of energy consumed as the bus10 travels from the current charging station 50 to the next.

In some embodiments, factors that may affect energy consumption of thebus 10 (e.g., weather, time of day, traffic, etc.) may also be includedin the determination of E_(MIN). For instance, on hot (i.e., ambienttemperature T_(AMBIENT)≥a first threshold temperature) or cold(T_(AMBIENT)≤a second threshold temperature) days and/or if snow ispresent or expected on the route 20, the control system 60 may increaseE_(MIN) to account for the additional energy that may be needed tooperate the HVAC system as the bus 10 travels between two successivecharging events. Similarly, if the time of day and/or trafficinformation indicates that the traffic is high on the route 20, thecontrol system 60 may increase E_(MIN) to account for possible trafficrelated delays. Additionally or alternatively, in some embodiments, afactor of safety (10%, 20%, etc.) may be added to the E_(MIN) calculatedin step 160 to account for unexpected factors that may increase energyconsumption.

The control system 60 may then determine whether E_(MAX) will beexceeded if the bus 10 is provided with the minimum amount of energy(E_(MIN)) it needs until the next charging event (e.g., energy needed tocomplete its route 20) (step 170). That is, in step 170, control system60 may check to determine if E_(USED)+E_(MIN)>E_(MAX). If it is not,then the bus 10 may be provided with an amount of energy equal toE_(MAX)+E_(USED) (i.e., the available amount of energy, E_(AVAILABLE),that can be consumed by the charging station without exceeding E_(MAX))at the default charging rate (step 180). It is also contemplated that,in some embodiments, the bus 10 may be provided with an amount of energyequal to E_(MIN) (i.e., the amount of energy it actually needs until thenext charging event) at the default charging rate in step 180. Providingan amount of energy equal to E_(MAX)−E_(USED), or E_(AVAILABLE), in step180 provides an additional amount of energy in excess of the actualamount of energy the bus needs until the next charging event (i.e.,E_(MIN)). If E_(USED)+E_(MIN) is greater than E_(MAX) (i.e., step 170 isYes) then the control system 60 may provide an amount of energy equal toE_(MIN) to the bus 10 at a reduced charging rate (step 190). Thisreduced charging rate may be such that the demand limit for thepredetermined time period (15 mins in this exemplary embodiment) is notexceeded. That is, the reduced charging rate may be selected such thatonly an amount of energy equal to E_(AVAILABLE) is provided to the bus10 in the remaining amount of time in the current time window(Δt=t₁₅−t_(i), in FIG. 4). The remaining amount of energy (i.e.,E_(MIN)−E_(AVAILABLE)) may be provided to the bus 10 after the expiry ofthe time window (i.e., after t₁₅ in FIG. 4). An exemplary embodiment ofstep 190 of FIG. 3A is explained in more detail in the embodimentdescribed below.

FIG. 3B illustrates another exemplary embodiment of charging the bus atthe charging station. In this embodiment, if E_(USED)+E_(MIN) is greaterthan E_(MAX) (i.e., step 170 of FIG. 3A is Yes), then the control system60 may provide an amount of energy equal to E_(AVAILABLE) (orE_(MAX)−E_(USED)) to the bus 10 in a time period At that extends to theremaining amount of time in the current time window (Δt=t₁₅−t_(i) inFIG. 4) (step 200). That is, an amount of energy equal to E_(AVAILABLE)may be transferred to the bus 10 at an energy transfer rate ofE_(AVAILABLE) /Δt. In some embodiments, in step 200, the control system60 may determine a value of current (I) that will provide an amount ofenergy equal to E_(AVAILABLE) in a time period (Δt) using the relationE−V×I×Δt, where V is the voltage. This de-rated value of current maythen be directed to the bus 10 by the charging head 30, That is, ifproviding the minimum amount of energy (E_(MIN)) to the bus 10 tocomplete its route 20 will cause the total energy consumed in the timewindow to exceed E_(MAX) (step 170 is YES), the control system 60 mayde-rate the current such that only the remaining energy available in thetime window is provided to the bus in that time window 300.

Since, the amount of energy equal to E_(AVAILABLE) is insufficient forthe bus to complete its route, the control system 60 may provideadditional energy (E_(ADDITIONAL)) to the bus after time window 300 endsand a new time window begins (step 210). Since the additional energy isonly provided after the time window 300 ends, the additional energy doesnot count towards the energy consumed in time period 300. The controlsystem 60 thus charges the bus without exceeding the power consumptionthat will trigger a rate hike (i.e., increases the demand billing rate).In some embodiments, this additional energy may be calculated based onthe default charging schedule (i.e.,E_(ADDITIONAL)=E_(NEED)−E_(AVAILABLE)), while in some embodiments,E_(ADDITIONAL) may be calculated based on the minimum energy needed tocomplete a route (i.e., E_(ADDITIONAL)=E_(MIN)−E_(AVAILABLE)). Theadditional energy may be provided at the default charging rate or at alower charging rate.

With reference to FIG. 4, in some geographic locations 70, a rollingtime window is used for utility cost calculations. In such embodiments,when a time window 300 ends, the time window slides to the right by apredetermined amount on the time axis to start a new time window. As thetime window slides to the right, portions of the energy consumptioncurve on the left end (e.g., all or a portion of section 310) of thetime window 300 drops out of the new time window freeing up more energythat can be consumed in this new time window. If this freed up energy inthe new time window is sufficient to provide E_(ADDITIONAL) to the bus10 at the default charging rate, the bus 10 may be charged in step 210at the default charging rate. If not, a lower charging rate (e.g., suchthat E_(MAX) for the new time window is not exceeded) may be selected.In some embodiments, the new time window may be positioned completely tothe right of a previous time window 300. That is, time t=0 for the newtime window may correspond to time t=15 of the previous time window 300.In such embodiments, starting a new time window effectively resets thecount of total energy used in the time period (i.e., E_(USED)=0), andthe bus 10 may be charged in step 210 at the default charging rate.

Several modifications are the possible for the disclosed method 100. Forexample, in some embodiments, if the control system 60 determines thatE_(USED)+E_(MIN) is greater than E_(MAX) (i.e., step 170=YES), then thecontrol system 60 may determine the energy needed by the bus (E′_(MIN))to travel to its next charging event with selected non-essential powerconsumption sources (HVAC, music, lights, etc.) deactivated. Thenon-essential power consumption sources may be selected based onconditions such as, for example, the time of day and/or the prevailingweather condition. For example, during day time, the interior/exteriorlights of the bus 10 may be considered to be a non-essential powerconsumption sources. The control system 60 may then determine ifE_(USED)+E′_(MIN) is greater than E_(MAX), and provide E^(′)MIN to thebus 10 if E_(USED)+E′_(MIN) is not greater than E_(MAX), beforeexecuting step 190. In some embodiments, a user (bus driver, supervisorat the transportation authority, etc.) may be given an option to bypassone or more steps in the method. For example, if the control system 60determines that E_(USED)+E_(MIN) is greater than E_(MAX) (i.e., step170=YES), then the control system 60 may allow the user to bypass (e.g.,by pressing a button, icon, etc.) the step of de-rating the current(i.e., step 200) and charge the bus with an amount of energy equal toE_(MIN) or E_(NEED). Other modifications that may be made to thecharging method 100 will be apparent to a person of ordinary skill inthe art.

The disclosed method identifies those charging events that will increasethe demand billing rate and adjust them so that the buses are chargedwithout triggering the increased demand billing rate. Since onlycharging events that affect the demand billing rate are selected foradjustment, the majority of the charging events remain unaffected. Someof the adjusted charging events are modified by eliminating excessamounts of charging and some are modified by extending the chargingevent to shift at least some of the energy consumption to a new timewindow. Since only those charging events that are extended affect theschedule of the buses, energy cost is reduced with minimal impacting thebus schedule. Modeling has indicated that, in an exemplarytransportation application, a reduction of about 20% in electricitybills for a month can be achieved by adjusting only 2.8% of the chargingevents in the month and causing minimal impact to the schedule.

While principles of the present disclosure are described with referenceto a fleet of electric buses, it should be understood that thedisclosure is not limited thereto. Rather, the systems and methodsdescribed herein may be employed to manage recharging of any electricvehicle. Those having ordinary skill in the art and access to theteachings provided herein will recognize additional modifications,applications, embodiments, and substitution of equivalents all fallwithin the scope of the embodiments described herein. Accordingly, theinvention is not to be considered as limited by the foregoingdescription. For example, while certain features have been described inconnection with various embodiments, it is to be understood that anyfeature described in conjunction with any embodiment disclosed hereinmay be used with any other embodiment disclosed herein.

1-20. (canceled)
 21. A method used by a control system to charge avehicle at a charging station in a geographic location, comprising:using, by the control system, a rolling time window of one or morecharging events of the vehicle at the charging station to avoidincreasing utility cost calculations of the one or more charging eventsby: sliding, when a first time window of the rolling time window ends,the rolling time window a predetermined amount along a time axis tostart a second time window of the rolling time window; dropping portionsof an energy consumption curve of the rolling time window as the rollingtime window drops out of the second time window thereby freeing upenergy capable of being consumed by the vehicle at the charging stationin the second time window; and upon determining that the freed up energyin the second time window is sufficient to provide an additional energy(E_(ADDITIONAL)) to the vehicle at a default charging rate withoutincreasing the utility cost calculations of the one or more chargingevents, charging the vehicle at the default charging rate.
 22. Themethod of claim 21, wherein the control system using the rolling timewindow further comprises: upon determining that the freed up energy inthe second time window is insufficient to provide the additional energy(E_(ADDITIONAL)) to the vehicle at the default charging rate, chargingthe vehicle at a lower charging rate than the default charging rate sothat that a maximum amount of energy (E_(MAX)) that can be consumed bythe charging station within the second time window is not exceeded. 23.The method of claim 21, wherein the control system using the rollingtime window further comprises: resetting a total energy count bystarting a third time window after the second window; sliding, when thesecond time window of the rolling time window ends, the rolling timewindow another predetermined amount on the time axis to start the thirdtime window of the rolling time window; dropping portions of the energyconsumption curve of the rolling time window as the rolling time windowdrops out of the third time window thereby freeing up energy capable ofbeing consumed in the third time window upon determining that the freedup energy in the third time window is sufficient to provide anotheradditional energy to the vehicle at the default charging rate, chargingthe vehicle at the default charging rate.
 24. The method of claim 21,wherein the utility cost calculations comprise a cost per unit of energyand accounts for a demand charge for energy consumed by the chargingstation.
 25. A method of using a control system to control charging ofone or more electric vehicles at one or more charging stations in ageographic locality, the method comprising: determining, by the controlsystem, a maximum amount of energy (E_(MAX)) that can be consumed by theone or more charging stations within a reference time window withoutincreasing a demand billing rate, E_(MAX) being determined based on aschedule optimization routine that considers a charging schedule of theone or more electric vehicles operating in the geographic locality andone or more vehicle-specific factors; determining, by the controlsystem, a total amount of energy already consumed (E_(USED)) by the oneor more charging stations in the reference time window by trackingE_(USED) between a first time and a second time in the reference timewindow and summing the tracked E_(USED) between the first time and thesecond time in the reference time window; determining, by the controlsystem, an amount of energy needed (E_(NEED)) by the one or moreelectric vehicles based on summing the tracked E_(USED) and E_(MAX). 26.The method of claim 25, wherein the step of determining, by the controlsystem, E_(USED) comprises determining the total energy consumed by eachof the one or more charging stations in the reference time window up toa current time.
 27. The method of claim 25, wherein the step ofdetermining, by the control system, E_(NEED) is further based on aresidual state-of-charge (SOC) of a battery capacity of the one or moreelectric vehicles before charging begins.
 28. The method of claim 27,further comprising: notifying, by the one or more vehicle, to thecontrol system a current SOC prior to, or after, docking with the one ormore charging stations.
 29. The method of claim 25, wherein the step ofdetermining, by the control system, E_(MAX) is calculated based onhistoric energy consumption data of the one or more electric vehicles.30. The method of claim 25, further comprising: upon determining, by thecontrol system, that E_(USED) and a minimum amount of energy (E_(MIN))needed by the one or more electric vehicles until a next charging eventis greater than E_(MAX), providing at a reduced charging rate an amountof energy to the one or more electric vehicles that is equal to E_(MIN).31. The method of claim 30, further comprising: determining, by thecontrol system, the reduced charging rate based on whether a demandlimit for the reference time window is exceeded.
 32. The method of claim30, further comprising: selecting, by the control system, the reducedcharging rate so that only an available amount of energy equal(E_(AVAILABLE)) is provided to the one or more electric vehicles in aremaining amount of time in the reference time window.
 33. The method ofclaim 32, further comprising: providing a remaining amount of energy tothe one or more electric vehicles after expiry of the reference timewindow.
 34. The method of claim 25, further comprising: upon determiningthat a minimum amount of energy (E_(MIN)) needed by the one or moreelectric vehicles until a next charging event will cause a total energyconsumed in the reference time window to exceed E_(MAX), de-rating acharge current so that only an available amount of energy equal(E_(AVAILABLE)) in the reference time window is provided to the one ormore electric vehicles.
 35. The method of claim 25, further comprising:upon determining that an amount of energy equal to an available amountof energy equal (E_(AVAILABLE)) in the reference time window isinsufficient for the one or more electric vehicles to complete a route,providing an additional energy (E_(ADDITIONAL)) to the one or moreelectric vehicles after the reference time window ends and a newreference time window begins.
 36. The method of claim 25, wherein thestep of determining, by the control system, the maximum amount of energy(E_(MAX)) comprises determining the maximum amount of energy (E_(MAX))capable of being consumed in the reference time window withouttriggering a rate hike.
 37. The method of claim 25, further comprising:generating, by the control system, an energy consumption curvecomprising a plurality of time periods of the reference time window,wherein each time period comprises points reflecting the one or morevehicles being charged prior to a current time and plateaus reflectingtime periods when the one or more charging stations is idlecorresponding to when the one or more vehicles are not being charged.38. The method of claim 21, further comprising: upon determining, by thecontrol system, that the E_(USED) and a minimum amount of energy(E_(MIN)) needed by the one or more electric vehicles until a nextcharging event is greater than E_(MAX), deactivating, by the controlsystem, energy for one or more non-essential power consumption sourcesof the one or more vehicles during travel to a next charging event. 39.The method of claim 38, wherein the non-essential power consumptionsources are deactivated by the control system based on a time of dayand/or a prevailing weather condition.
 40. A charging station for anelectric vehicle, comprising: charging electrodes configured toelectrically couple with charge-receiving electrodes of an electricvehicle during a charging event; and a control system configured to: usea rolling time window of one or more charging events of the vehicle atthe charging station to avoid increasing utility cost calculations ofthe one or more charging events by: sliding, when a first time window ofthe rolling time window ends, the rolling time window a predeterminedamount along a time axis to start a second time window of the rollingtime window; dropping portions of an energy consumption curve of therolling time window as the rolling time window drops out of the secondtime window thereby freeing up energy capable of being consumed by thevehicle at the charging station in the second time window; and upondetermining that the freed up energy in the second time window issufficient to provide an additional energy (E_(ADDITIONAL)) to thevehicle at a default charging rate without increasing the utility costcalculations of the one or more charging events, charging the vehicle atthe default charging rate.